Method of casting propeller-wheels



T. 0. THACHER.

METHOD OF CASTING PROPELLE-B WHEELS. APPLICATION- FILEDOCT. 24,1918-RENEWED DEC. 30, 1919.

1,330,661. Patented Feb. 10,1920.

, 3 SHEETSSHEET 1.

.9 v awue mtoz T. 0. THACHER. METHOD OF CASTING PROPELLER WHEELS.

APPLICATION FILED OCT. 24. I918- RENEWED DEC- 30,1919.

Patented Feb. 10,1920.

3 SHEETS-SHEET 2.

T. 0. THACHER.

METHOD OF CASTING PROPELLER WHEELS.

RENEWED DEC. 30,

APPLICATION FILED OCT- 24, l9l8. 1,330,661

Patented Feb. 10, 192.0.

3 SHEETSSHEET 3.

La-:11 F5 UNT STAEg FATENT OFFICE.

THOMASOXENBEIDGE TEACHER, OF ALBANY, NEW YORK, ASSIGNOR T0 TEACHERPROPELLER, AND FOUNDRY COPUPGBATION, OF ALBANY, NEW YORK, A CORPO-RATION 0F NEVT YORK.

METHOD OF CASTING PROPELLER-WHEELS.

issoreei.

Application filed October 24, 1918, Serial No. 259,45 -3.

To all whom it may concern:

Be it known that I, Trro rAs O. THAGT-IER, a citizen of the UnitedStates, residing at Albany, in the county of Albany, State of New York,have invented certain new and useful Improvements in Methods of CastingPropeller-Wheels; and I do hereby declare the following to be a full,clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

This invention relates to methods and apparatus for casting propellerwheels, par ticularly large propellers for ocean steamships, and has forits object to produce a cast propeller wheel which will be so accurately symmetrical in the position, pitch and dimensions of its bladesas to require little or no machining to secure a balanced finishedpropeller.

A further object of the invention is to provide a method and anapparatus for casting propeller wheels whereby the propeller wheels maybe properly made by ordinary foundrymen without special care or accuratecalibration in the setting of the molds, so that the speed of productionis much increased and the cost of manufacture correspondingly reduced.

A further obiect of the invention is to provide a method of casting;propeller wheels which provides a smooth surface for the blades in theoriginal casting so that the blades do not require a surface finishingas is usually necessary to prevent excessive skin friction of thepropeller when in use. I Y

My invention also embodies an improved method of pouring the castingwhereby the complete filling of the mold with clean metal withoutcontraction is secured even in the large wheels of fifteen feet orgreater diameter.

My invention also provements in the whereby the process carried out.

By the method of castingnow practised, large propellers are formed froma pattern consisting of a single blade and hub, the hub being mountedfor rotation on a vertical spindle set in the middle of the pit in whichthe wheel is to be cast. A set of includes certain imapparatus employedmay be successfully Specification of Letters Patent.

Patented Feb. 10, 1920.

Renewed. December 30, 1919. Serial No. 348,383.

flasks, one for each blade, is grouped around the spindle in theapproximate positions of the blades and filled with green sand. Thefoundryman then places the pattern over one of the flasks and rams thesand around the pattern to form the impression for that blade. Thepattern is then lifted from that flask and turned through the anglerequired by the number of blades to be formed, to a position over thenext flask and the process repeated for each blade. The accuracy of thepitch and balance of the propeller are thus dependent almost wholly onthe skill of the workman casting that particular propeller and thewheels cast by inexperienced workmen are frequently so out of true as tobe unfit for use.

My improved method of casting consists in employing a separate andidentical mold for each blade and locking the blade molds together inaccurately radial and properly spaced positions around their commoncenter, the positioning of the blade molds being obtained by means of abed plate having an accurately machined surface and accuratelypositioned holes or bearings interlocking with similarv surfaces andholes or projections carried by the separate molds.

In order that the impressions of the blades in the molds may beidentical in shape and location the molds are preferably formed inseparate flasks from the same pattern or box, the flasks and the patternbox being all divided with each half of the pattern box designedtointer-lock with one half of the flask. The flasks in turn interlockwith the holes or projections of the base plate so that if the plate isaccurately made and finished the propeller will necessarily besymmetrical if the method has been properly followed.

The flasks containing the blade molds are set up on the bed plate arounda bottom core attached to the center of the plate and fixed in positionby means of bolts in the registering holes which determinetheir-accurate positioninpg. The meeting edges of the several molds arethen sealed with slurry to avoid fins on the finished casting and themold is then closed with suitable center cores for forming the hub andis ready for the mold to be poured.

In the accompanying drawings I have illustrated my improved apparatusand also the manner of using the apparatus in carryin out the improvedmethod.

*igure 1 is a plan view of the flask employed for the blade molds;

Fig. 2 is a plan view of the part of the pattern box used with the lowerpart of the flask;

Fig. 3 is a sectional view showing the arrangement of the lower part ofthe flask and its pattern box pattern to receive the sand mixture;

Fig. l is a cross section on line H of Fig. 3;

Figs. 5 and 6 are sectional views similar to Fig. 3 showing furthersteps in the method of forming the molds;

Fig. 7 is a plan view of the other half of the pattern box;

Fig. 8 is a sectional view showing the upper half of the flask and itscomplementary part of the pattern box ready to receive the sand mixture;

Fig. 9 is a sectional view showing the two parts of the flask assembled;

Fig. 10 is a sectional view on line 1010 of Fig. 9;

Figs. 11 and 12 are, respectively, a central vertical section and a planview of the assembled molds and cores set up to be poured according tomy improved method; and

Fig. 13 is a sectional detail of the trough through which the metal ispoured.

The separate flasks for each propeller blade are identical and are madein halves in the usual manner, the line of division between the twohalves being near one face as indicated at a Fig. 10. The flanges of themeeting edges of the two halves are of substantial width and aremachined off to true horizontal surfaces, and the upper and lower facesof the flask which are also flanged, are machined ofl to true surfacesparallel with the surfaces of the flanges.

At the inner end of the flask, that is. the end of the flask in whichthe hub end of the blade will be formed, the side walls of the flask areinclined as here shown at an angle of 45 degrees to the middle line ofthe flask, the angle depending upon the number of blades of theparticular propeller to be cast. Each of the inclined faces is providedwith sandretaining projections 26, the ends of which are accuratelymachined off so that their end faces form flat surfaces lying in planesvertical with respect to the machineflnished horizontal faces of theflask and at such angles to the middle line of the flask that theintersections of the two surfaces formed by the ends of the projectionsaccurately coincide at the center of the propeller.

At the outer end of the flask, that is, the end toward which the tip ofthe blade will extend, each half of the flask has a projecting ear 6 inwhich is bored a hole 25, the holes being accurately positioned in themiddle line of the flask as determined by the inclined end faces and ata predetermined distance from the center as determined by theintersection of the inclined surfaces. Each half of the flask is alsoprovided with holes 30 in its flange for receiving the clamping boltswhich hold the two parts of the flask together.

The two halves of the pattern box are shown in Figs. 2 and 7, the part27 shown in Fig. 2 cooperating with the deeper portion of the flask toform one half of the di vided mold while the other two parts of thepattern box and flask are used together to form the other half of themold. The part 27 of the pattern box comprises a back plate 28 with thepattern block 29 attached thereto. The face of the plate to which theblock is attached is accurately machined to a trxie surface and thepattern block is built up to the desired pitch line from the surface ofthe plate as a base. Formed in the back plate around its margins are aseries of holes corresponding to the holes in the margins of the flask,and there is also provided a middle hole in the end of the platecorresponding with the holes 25 in the ears at the ends of the flasks,the holes being accurately positioned on the center line of the patternblock so that when the portion of the flask and the corresponding halfof the pattern box are fastened together by bolts through theregistering holes, the pattern will be positioned to form the bladeimpres- Isgion accurately in the center of the pattern The inner end ofthe pattern block is shaped to form the impression of the proportionalpart of the hub for one blade, that is, a sector of 90 degreesamplitude, by means of two upright plates 32 attached to the pattern boxwith their inner faces ac- .curately finished off and positioned so thatwhen the flask and pattern box are clamped together the ends of all theprojections 26 of the flask will abut against the faces of the uprightplates and the line of intersection of their faces will correspond withthe axis of rotation of the propeller. The pattern box is also providedwith a detachable pattern piece 26 for forming a recess in the blademolds to receive the bottom center core which will be later described.

After the parts of the flask and pattern box are clamped together asshown in Figs. 3 and 4 the sand mixture is rammed in through theopenings in the top of the flask. A plate 33 having a machine-finishedsurface is then pressed down on top of the flask and clamped thereto asshown in Fig. 5,

the flask. The connected flask and pattern box parts with the plateclamped to the flask are then inverted and the pattern box partunclamped and withdrawn, the piece 26 being first detached and removed.The flask part containing the molded sand mixture is then placed in anoven and baked in the usual manner, forming a half mold for thepropeller blade with true surfaces on its bottom and inner end faces,and its flanged edges, and with the blade impression accurately locatedin the flask with reference to the surfaces and the bolt holes.

The other half of the mold is formed in the same manner in the upperpart of the flask from the half of the pattern box shown in Fig. 7, thishalf of the pattern box being provided with sidewalls against which theedges of the upper part of the flask are clamped as shown in Fig. 8. Thetwo half molds, when fitted together as shown in Figs. 9 and 10, form acomplete mold for a single blade and its proportionate part of the hub.

Identical molds are formed from the same pattern box for each of theblades. The blade molds are then assembled on the base or bed plate 1which is of greater diameter than the over all dimensions of thepropeller and is securely fixed in the ground, preferably in a pit deepenough for the top of the flasks to be flush with the surface. To reduce the weight of the plate without sac rifice of rigidity it may beformed as shown,

' of closely spaced bars 2 with connecting cross bars 3, the uppersurface of the bars 2 being machined off to present a true surface.

At the exact center of the plate is provided a bearing or recess 36 toreceive a corresponding projection formed on the bottom plate of abottom center core 37 shown in Fig. 11, the core consisting of a rounddisk of sand mixture baked to the top of the plate and of a diameter tofit in the recesses formed in the inner ends of the blade molds by thedetachable pieces 26 of the pattern blocks when the blade molds aregrouped around the center of the plate in the manner shown in Fig. 11.

At equidistant points around the circumference of the plate there isprovided a series -of holes 5 corresponding in number to the number ofthe propeller blades, the holes being spaced from the center of theplate to correspond with the holes in the ends of the flasks so thatwhen the flasks are assembled on the plate in the manner shown and holesin the flasks are accurately registered with those in the plate, theflasks will be properly positioned to produce an accurately symmetricalpropeller.

The flasks are positioned around the plate by pins dropped through theholes in the ends of the flasks and may, if desired, be further lockedby means of bolts through the flanges of the flasks, but for largepropellers the weight of the flasks is so great that there is no dangerof any liability of displacement after they have once been set inaccurate position.

After the flasks are positioned the joints between the meeting edges ofthe several blade molds and the bottom core are closed with slurry orother suitable mixture for the purpose, access being had to the interiorof the mold through the opening at the top which at this time has notbeen closed. After the seams have been closed a center core 38 forforming the shaft opening in the hub of the propeller, of the shapeshown in Fig. 11, is inserted through the top opening, the taperedbottom end of the center core fitting a corresponding recess in thecenter of the bottom core. The top opening is then closed with adisk-shaped top core 39 which fits into the recess at the top and themetal is ready for pouring.

The pouring may be effected by any suitable method, but for the bestresults I prefer to employ my improved method of pouring illustrated inFigs. l1, l2 and 13. To this end the upper halves of the blade molds areprovided near the tips of the blades with holes or passages 40 and thetop core 39 is also provided with holes, one or more for each blade.Rods (not shown) are set in the holes projecting above the top of the assembled flasks and green sand is filled in the pit around the mold andpiled up on top of the mold as indicated at 41. I then set in the sandtwo rectangular frames 42 long enough to reach from the end of one bladeto the end of the adjacent blade, as indicated in dot and dash lines inFig. 12, and the sand is then shaped around these frames 42 to formtroughs 4a to receive the metal from the ladles. A frame 43 is also setover the center of the mold, and a middle trough 45 is formed with theframe at?) to provide a basin into which the metal can rise. The rodsare then Withdrawn, leaving open passages leading from the ends of thetroughs 44 into the end of each blade mold and exit passages leadinginto the middle basin 45.

To skim the metal as it is poured each trough 44: is divided into threecompartments by means of transverse partitions 46 indicated in F 13, thepartitions being provided with passages 47 leading from the bottom ofthe middle compartment into the end compartments. The metal is thenpoured into the middle compartment, the dirt and impurities which arelighter than the molten metal, rising to the top, and the clean metalfrom the bottom overflowing through the passages 47 into the endcompartments when the level in the middle compartment rises above theupper ends of the passages opening into the end compart ments. From theend compartments, the

clean metal flows through the above1nentioned delivery passages into theends of the blade molds.

It will be noted that the blade molds are set so as to inclinedownwardly toward the ends so that the mold is filled at the lower ends,the metal "adually rising in the molds so that any loose particles inthe mold will rise with the rising level of the metal and fiow to thecenter. As the mold fills up the level of the metal rises in the hubopening and into the holes in the top core, thence overflowing into themiddle basin, so that when the mold is filled there will be a pressureon the metal due to the head provided for by the elevation of thetroughs and the receiving basin, thereby avoiding all shrinkage as themetal solidifies in the mold.

I have found in practice that a propeller cast by this method will be soaccurately symmetrical in balance and pitch of its blades as to requireno finishing after the propellers are removed from the mold. By usingbaked molds and cores for all parts of the propeller a much smoothersurface is obtained than can be had with green sand molds, and byclosing the joints in the mold after it is set up the casting isfreefrom fins throughout. In recently cast propellers of more than tenthousand pounds weight, the weight of the finished propeller showed avariance of less than one-tenth of one per cent. of the theoreticalweight.

It will be observed that with the bed plate and flasks and pattern boxesonce accurately constructed, no further calibration or adjustment isrequired to set up the mold, and any number of propellers, each an exactduplicate of the other, may be successfully cast in the same apparatus.

As pointed out above, the molds are set with the driving face of thepropeller downward. This arrangement not only permits the metal to bepoured at the ends of the blades in the manner described but alsoinsures a smooth solid surface on the driving face of the blades, forthe reason that any dirt in the blade molds which should not be carriedout through the risers at the center will of necessity rise to the topof the blade mold which shapes the back of the propeller.

I have shown and described my improved method as used for casting afour-blade propeller, but it will of course be understood that apropeller having any number of blades may be cast in the same manner byemploying flasks with their inclined faces at the proper angle for theparticular number of blades desired.

I claim:

1. The method of forming molds for east ing propellers which consists informing separate and identical blade molds for each blade, each moldhaving a portion of its exterior accurately finished with the impressionfor the blade accurately positioned with relation to such portion, andthen assembling the molds upon a previously prepared bed having aportion accurately finished for cooperation with the accurately finishedparts of the blade molds, said finished bed portion being positioned onthe bed so that when the blade molds are assembled on the bed with thecooperating parts in registration the impressions for the blades will besymmetrical with relation to a common center.

2. The method of forming molds for easting propellers which consists informing separate and identical blade molds for each blade, each moldhaving an accurately finished exterior surface and a fastening part withthe impression for the blade accurately positioned with relation to suchsurface and part, and then assembling the molds upon a previouslyprepared bed having accurately finished surface portions for cooperationwith the accurately finished surfaces and also having fastening partsfor cooperation with the fastening parts on said molds, the fasteningparts on said bed being symmetrically located on the bed With respect toa common center.

3. The method of forming molds for casting propellers which consists inproviding a series of identical flasks, one for each blade, each. flaskhaving an accurately finished surface and a locating part, formingidentical blade molds in said flasks with the blade impression inidentical and accurate relation to said surface and part, and thenassembling said flasks on a bed plate having an accurately finishedsurface for cooperation with the finished surfaces on the flasks andaccurately positioned locating parts for cooperation with the locatingparts of the flasks symmetrically arranged with respect to a commoncenter.

14:. The method of forming molds for casting propellers which consistsin setting up a bed plate having a machinefinished surface and a seriesof accurately located holes symmetrically arranged around a com moncenter, forming a set of identical blade molds one for each blade, withan accurately finished exterior surface and fastening part accuratelylocated with respect to the blade impression and setting up the blademolds on the bed plate with their position accurately determined by theholes in the bed plate.

The method of forming molds for easting propellers which consists inproviding a two-part pattern box, each part having an accuratelyfinished surface surrounding the blade pattern and with the bladepattern accurately positioned with respect to said surface, and a set ofidentical two-part flasks having accurately finished margins aroundtheir open sides and their opposite exterior faces also accuratelyfinished, then forming a series of identical blade molds in said flasksfrom the same pattern box by positioning the pattern-box parts on thecooperating flask portions with the finished margins of the pattern boxparts clamped to the finished margins of the flask parts to accuratelyand identically locate the blade impression in the flasks, and thenassembling said flasks on a bed plate having an accurately finishedsurface for cooperation with finished surfaces on the flasks inpositions determined by previously formed registering holes in the bedplate and flasks.

6. The method of forming molds for casting propellers which consists insetting up on a previously prepared bed plate a series of identicalflasks each having a baked blade mold with the impression for the bladeaccurately positioned in the flasks, and fasten-- ing the flasks to thebed plate by means of previously located holes in the flasks and bedplate, with the ends of the flasks grouped together at a common centerand with the blade impressions symmetrical with respect to said center.

7. The method of casting propellers which consists of setting up aseries of identical blade molds with the ends of the blade molds groupedtogether around a common center, said blade molds having their meetingends formed to provide a central hub opening, then filling the mold withmolten metal by simultaneously pouring the metal into the outer ends ofall the blade molds from an elevation to maintain a head on the metaland causing the metal to rise through the common central opening into anelevated receptacle, thereby providing a back pressure on the metal totake up the contraction.

8. The method of casting propellers which consists of setting up aseries of identical blade molds with the ends of the blade molds groupedtogether around a common center, said blade molds having their meetingends formed to provide a central hub opening, then filling the mold withmolten metal by means of a trough positioned. above the molds, thetrough having a receiving portion and also having a discharge portioncommunicating with the mold and an upwardly inclined feed orifice withinits confines leading from itsreceiving portion to said discharge portionso that the metal Wlll be taken from the bottom of the trough and willflow only when a predetermined level is maintained in the trough.

9. An apparatus for forming molds for casting propellers comprising abed plate having a finished surface and also having accurately locatedfastening means symmetrically positioned with respect to a commoncenter, a series of flasks for the blades w th accurately finishedsurfaces for cooperation with the surface of the plate with their innorends shaped to engage when the flasks are grouped around the previouslydetermined center of the plate, and'accurately located fastening meanson the flasks for cooperation with the fastening means on the plate andpositioned to maintain the flasks in position.

10. An apparatus for casting propellers comprising a bed plate having amachinefinished surface, a series of fastening means accuratelypositioned around a common center on the plate, a series of two-partflasks having their bottom faces and their meeting edges machined totrue surfaces, said flasks having their inner ends shaped to fit together at the common center when symmetrically arranged on the plate,and fastening means on each flask for cooperation with the fasteningmeans on the plate for maintaining the flasks in position, and a patternbox for forming identical blade cores in each flask, said pattern boxconsisting of two parts for cooperation respectively with the two partsof the flasks and each part comprising a machine-finished back platewith its pattern block accurately posltloned thereon, said back platehaving fastening means cooperating with the fastening means on the flaskparts for accurately positioning the blade impression in the mold.

11. In the method of forming molds for casting propellers, the steps ofproviding a two-part pattern box, each part having a blade patternaccurately positioned upon it, and a set of identical two-part flasks;forming each half of a blade mold by clamping together one part of thepattern box and the corresponding part of the flask, ramming the sandmixture thereinto upon the pattern, then inverting the flask and patternbox parts unclamping the pattern box parts, and baking the flask-partcontaining the molded sand mixture; and fitting together the two flaskparts with their attached half molds to form a flask having within it acomplete mold for a single blade.

12. In the method of forming molds for casting propellers, the steps ofproviding a two-part pattern box, each part having a blade patternaccurately positioned upon it, and a set of identical two-part flasks,forming each half of a blade mold by clamping together one part of thepattern box and the corresponding part of the flask, ramming the sandmixture thereinto upon the pattern, then inverting the flask and patternbox parts, unclamping the pattern box part, and baking the flask partcontaining the molded sand mixture; fitting together the two flask partswith their attached half molds to form a flask having within it acomplete mold for a single blade; repeating the mold-forming operationsto obtain from the same pattern box a set of identical blade molds, onefor each blade; and assembling the flasks containing the blade moldssymmetrically about a common center with the mold cavities accuratelypositioned with respect to said center.

13. In the method of forming molds for casting propellers, the steps ofproviding a two-part pattern box, each part having a blade patternaccurately positioned upon it, and a set of identical two-part flasks,each flask having an accurately finished surface and a locating part;forming each half of a blade mold by clamping together one part of thepattern box and the corresponding part of the flask, ramming the sandmixture thereinto upon the pattern, then inverting the flask and patternbox parts, unclamping the pattern box part, and baking the flask partcontaining the molded sand mixture; fitting together the two-flask partswith their attached half molds to form a flask having within it acomplete mold for a single blade; repeating the mold-forming operationsto obtain from the same pattern box a set of identical blade molds, onefor each blade; and then assembling the flasks containing the blademolds on a bed plate having an accurately finished surface forcooperation with the finished surfaces on the flasks and accuratelypositioned locating parts for cooperation with the locating parts on theflasks symmetrically arranged with respect to a common center;

14. The method of forming molds for casting propellers which consists inproviding a series of flasks, one for each blade, each flask having anaccurately finished surface, forming identical blade molds in saidflasks with the blade impressions in accurate relation to said surfaceand then assembling said flasks on a bed having an accurately finishedsurface for cooperation with the finished surfaces on the flasks, withthe flasks symmetrically arranged with respect to a common center.

15. The method of forming molds for casting propellers which consists inattaching a pattern box part to the open side of a flask part inaccurately predetermined position, said pattern box part having apartial blade pattern accurately positioned with respect to the portionclamped to the flask part, then filling the flask part with sandmixture, similarly forming in the complementary flask part a mold of thereverse side of the blade with the blade impressions in the flask partsso positioned with respect to each other as to accurately register whenthe flask parts are connected together, similarly forming a blade moldfor each blade of the propeller, then assembling the flasks on apreviously prepared bed with the blade impressions symmetrical withrespect to a common center.

16. An apparatus for forming molds for casting propellers, comprising abed having an accurately finished surface and a series of flasks, onefor each blade, having accurately finishee exterior surfaces forcooperati on with the surface of the bed whereby the flasks will occupyexact predetermined rela tive positions when assembled around a commoncenter on said plate.

17. An apparatus for forming molds for casting propellers, comprising abed having an accurately finished surface and a series of flasks, onefor each blade, having accurately finished exterior surfaces forcooperation with the surface of the bed whereby the flasks will occupyexact predetermined relative positions when assembled around a commoncenter on said plate, and a sectional pattern box comprising sectionshaving impression forming surfaces and accurately finished locatingsurfaces, said locating surfaces being accurately positioned withrespect to said mold forming faces, said flasks having surfaces finishedfor cooperation with said locating surfaces on the pattern box sectionto thereby locate the blade impressions accurately in said flasks.

In testimony whereof I aflix my signature.

THOMAS ()XENBRIDGE THACHER.

